Proposed work will be an extension of studies for human growth hormone as a family of proteins. Two aspects of the hypothesis are under scrutiny; the first is that these are multiple intact or single chain sequences, and the second is that one or more of these single chain sequences undergoes cleavage to an activated two-chain form, in analogy to the pro-insulin conversion to insulin. The final goal is to identify the identities and functions of the circulating forms. The development of radioimmunoassays and radio receptors is the means we employ to identify pituitary and circulating forms in whole plasma and in fractionated plasma. The applications to health problems will focus on growth problems, breast cancer, and diabetes mellitus. The diabetes aspects have developed with newer evidence that cleavage of growth hormone enhances insulinotropic actions. We propose to use physiological stimuli to growth hormone and prolactin secretion--sleep and exercise.